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TXFlyGuy

Well Known Member
Should we go with a dual Garmin EFIS, or use another brand as a secondary backup display?

Two G3X Touch displays vs. a single G3X and a GRT.
 
While rare, there have been reports of a software error bringing down multiple displays simultaneously. My vote is for a completely independent, including software, back-up.
 
BobTurner said:
While rare, there have been reports of a software error bringing down multiple displays simultaneously. My vote is for a completely independent, including software, back-up.
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With the dual Garmin G3X, we would also have dual ADAHRS. And independent battery backup.
 
With 2 screens, dual ADAHRS's and back-up power and serial buses, I think the chance of a dual failure is EXTREMELY remote.
 
Two additional issues to consider:

1) Two different brands of EFIS will mean two different user interfaces which could add to the workload during a partial panel event.

2) A single chart subscription for the G3X will work for all G3X displays in a single plane. Installing two different brands of EFIS could result in the need for multiple chart subscriptions (depending on brand and vfr/ifr).
 
Long ways to really worry about my panel... However I do it anyways! Is it silly to do two Panels and maybe a set of 3 backup steam gauges; airspeed, AI, alt?
 
Walt said:
With 2 screens, dual ADAHRS's and back-up power and serial buses, I think the chance of a dual failure is EXTREMELY remote.
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That's what I thought until I read this:

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1445144163

While I wouldn't expect this to happen much, it does happen and I plan to have a backup AI (probably the Dynon D2) at a minimum. I'd hate to be climbing or descending through clouds when the displays decided to reboot!
 
Mark Dickens said:
That's what I thought until I read this:

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1445144163

While I wouldn't expect this to happen much, it does happen and I plan to have a backup AI (probably the Dynon D2) at a minimum. I'd hate to be climbing or descending through clouds when the displays decided to reboot!
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Does this apply equally to Garmin? Note the above is a Dynon issue.

How about ForeFlight with Stratus 2S as a backup? And, adding a second or third display increases your odds of a failure by 100 or 200%.
 
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When we do systems safety analysis for certified airplanes, common software across otherwise independent hardware systems is considered a common mode failure. The principle concern (and it has been demonstrated) is that the 2 independent systems doing the exactly same thing at the same time will execute the same faulty code and both systems will fail in the same way. Actually total failures aren't the most critical, is is the misleading failures without warning. Say, bad altitude data that shows you 300 ft higher than you are when on an ILS.

That is why software on certified systems that provide critical functions goes through rigorous verification and testing that costs lots of money.

The uncertified systems we use in experimental airplanes don't go through the rigorous DO-178 software verification process, and we hope they are developed and tested by responsible organizations.
 
Thanks

Glad to see this topic. I am leaning toward the second g3x once I prove that I can install the one I'm working on now and I like it.

My question and concern re the dual g3x is, for a software upgrade, is it going to instantly be installed on both displays and therefore remove the redundant property? Or will it be possible to install on only one display at a time so that if there is a problem you still have one that should work? I am assuming, like with the dynon example, that an upgrade has a bug that creates a problem.
 
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TXFlyGuy said:
Does this apply equally to Garmin? Note the above is a Dynon issue.

How about ForeFlight with Stratus 2S as a backup? And, adding a second or third display increases your odds of a failure by 100 or 200%.
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This is exactly how I'm planning on backing up my 3 screen G3X touch system, once I start my IFR training. Right now, the backup if the entire G3X system fails is looking out the window!
 
Jimd said:
Glad to see this topic. I am leaning toward the second g3x once I prove that I can install the one I'm working on now and I like it.

My question and concern re the dual g3x is, for a software upgrade, is it going to instantly be installed on both displays and therefore remove the redundant property? Or will it be possible to install on only one display at a time so that if there is a problem you still have one that should work? I am assuming, like with the dynon example, that an upgrade has a bug that creates a problem.
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You need to update both screens at the same time, as the screens, adhrs, engine monitors, auto pilot servos all work together as a single "system". The screen software updates the firmware of all of the other G3X components as well.
 
RVDan said:
The uncertified systems we use in experimental airplanes don't go through the rigorous DO-178 software verification process, and we hope they are developed and tested by responsible organizations.
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The responsible organization is YOU, the builder and/or pilot. There are infinite possible combinations of hardware and software in any given experimental aircraft, so it would be impossible to test for all outcomes. This is why it is imperative that you test all software updates in VFR conditions before heading out to fly in the clouds. I don't care what brand of avionics you have! Airlines don't have the luxury of performing software test hops before they go hard IFR, but you do.

I think having two separate brands for primary EFIS boxes would be confusing for the pilot(s) in daily use. In 2011 we built a few LSAs with a GRT primary screen (and GRT engine instruments) with a Garmin GDU 375 MFD because the GRT primary instruments and engine instruments were better than the Garmin, and the Garmin map was better than the GRT map. It was great at first but training customers how to use the combo was difficult. Nowadays, GRT maps are improved and Garmin primary/engine instruments are improved, so we stick with one brand or the other in each plane. Additionally, the boxes of common brands communicate with each other to ease pilot workload.

A single-brand total EFIS system with dual main screens, dual AHRS and battery backup, with the system backed up by a small independent EFIS with its own battery such as a GRT Mini would be an ideal situation in most IFR experimental aircraft. If a software update comes out for the main system and you are worried about software taking it down, then don't update the software in the small backup unless the main system is fully proven, and vice versa.

And, adding a second or third display increases your odds of a failure by 100 or 200%.
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In a more complex system the odds of having SOMETHING fail are greater, but in a properly designed system, your odds of having a failure that affects the safe outcome of the flight are much, much less.
 
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